Lithographic apparatus and device manufacturing method

ABSTRACT

A programmable patterning structure for use with a lithographic projection apparatus according to one embodiment of the invention includes a plurality of reflective elements A, B, C, each reflective element having two distributed Bragg reflectors  51, 52.  A separation D 1  between the two distributed Bragg reflectors is adjustable between a first relation, at which destructive interference between reflections from the first and second distributed Bragg reflectors  51, 52  results in substantially zero reflectivity, and a second relation, in which constructive interference between reflections from the first and second distributed Bragg reflectors  51, 52  results in high reflectivity.

This is a continuation of U.S. patent application Ser. No. 10/613,218,filed Jul. 7, 2003 which is now U.S. Pat. No. 6,864,958, which claimspriority to European Application No. 02254786.3, dated Jul. 9, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to lithographic apparatus and methods.

2. Background Information

The term “programmable patterning structure” as here employed should bebroadly interpreted as referring to structure that may be used to endowan incoming radiation beam with a patterned cross-section, correspondingto a pattern that is to be created in a target portion of the substrate.The terms “light valve” and “spatial light modulator” may also be usedin this context. Generally, such a pattern will correspond to aparticular functional layer in a device being created in the targetportion, such as an integrated circuit or other device (see below).Examples of such programmable patterning structure include:

A programmable mirror array. One example of such a device is amatrix-addressable surface having a viscoelastic control layer and areflective surface. The basic principle behind such an apparatus is that(for example) addressed areas of the reflective surface reflect incidentlight as diffracted light, whereas unaddressed areas reflect incidentlight as undiffracted light. Using an appropriate filter, theundiffracted light can be filtered out of the reflected beam, leavingonly the diffracted light behind; in this manner, the beam becomespatterned according to the addressing pattern of the matrix-addressablesurface. An alternative embodiment of a programmable mirror arrayemploys a matrix arrangement of very small (possibly microscopic)mirrors, each of which may be individually tilted about an axis byapplying a suitable localized electric field, or by employingpiezoelectric actuation means. The mirrors may be matrix-addressable,such that addressed mirrors will reflect an incoming radiation beam in adifferent direction with respect to unaddressed mirrors; in this manner,the reflected beam is patterned according to the addressing pattern ofthe matrix-addressable mirrors. The required matrix addressing can beperformed using suitable electronic circuitry. In both of the situationsdescribed hereabove, the patterning structure can comprise one or moreprogrammable mirror arrays. More information on mirror arrays as herereferred to can be gleaned, for example, from U.S. Pat. Nos. 5,296,891and 5,523,193, which are incorporated herein by reference, and PCTpatent applications WO 98/38597 and WO 98/33096, which are incorporatedherein by reference. In the case of a programmable mirror array, thesupport structure for the array may be embodied, for example, as a frameor table which is fixed or movable as required.

A programmable LCD array. An example of such a construction is given inU.S. Pat. No. 5,229,872, which is incorporated herein by reference. Asabove, the support structure in this case may be embodied, for example,as a frame or table which is fixed or movable as required.

For purposes of simplicity, the rest of this text may, at certainlocations, specifically direct itself to examples involving a mask (or“reticle”) and mask table; however, the general principles discussed insuch instances should be seen in the broad context of the patterningstructure as hereabove set forth.

Lithographic projection apparatus may be used, for example, in themanufacture of integrated circuits (ICs). In such a case, the patterningstructure may generate a circuit pattern corresponding to an individuallayer of the IC, and this pattern can be imaged onto a target portion(e.g., comprising one or more dies) on a substrate (e.g., a wafer ofsilicon or other semiconductor material) that has been coated with alayer of radiation-sensitive material (resist). In general, a singlewafer will contain a network of adjacent target portions that aresuccessively irradiated via the projection system (e.g., one at a time).

Among current apparatus that employ patterning by a mask on a masktable, a distinction can be made between two different types of machine.In one type of lithographic projection apparatus, each target portion isirradiated by exposing the entire mask pattern onto the target portionat once; such an apparatus is commonly referred to as a wafer stepper.In an alternative apparatus—commonly referred to as a step-and-scanapparatus—each target portion is irradiated by progressively scanningthe mask pattern under the projection beam in a given referencedirection (the “scanning” direction) while synchronously scanning thesubstrate table parallel or anti-parallel to this direction. Since, ingeneral, the projection system will have a magnification factor M(generally <1), the speed V at which the substrate table is scanned willbe a factor M times that at which the mask table is scanned. Aprojection beam in a scanning type of apparatus may have the form of aslit with a slit width in the scanning direction. More information withregard to lithographic devices as here described can be gleaned, forexample, from U.S. Pat. No. 6,046,792, which is incorporated herein byreference.

In a manufacturing process using a lithographic projection apparatus, apattern (e.g., in a mask) is imaged onto a substrate that is at leastpartially covered by a layer of radiation-sensitive material (resist).Prior to this imaging step, the substrate may undergo variousprocedures, such as priming, resist coating and a soft bake. Afterexposure, the substrate may be subjected to other procedures, such as apost-exposure bake (PEB), development, a hard bake andmeasurement/inspection of the imaged features. This array of proceduresis used as a basis to pattern an individual layer of a device, e.g., anIC. Such a patterned layer may then undergo various processes such asetching, ion-implantation (doping), metallization, oxidation,chemo-mechanical polishing, etc., all intended to finish off anindividual layer. If several layers are required, then the wholeprocedure, or a variant thereof, will be repeated for each new layer.

Eventually, an array of devices will be present on the substrate(wafer). The devices are then separated from one another by a techniquesuch as dicing or sawing, whence the individual devices can be mountedon a carrier, connected to pins, etc. Further information regarding suchprocesses can be obtained, for example, from the book “MicrochipFabrication: A Practical Guide to Semiconductor Processing,” ThirdEdition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN0-07-067250-4.

The term “projection system” should be broadly interpreted asencompassing various types of projection system, including refractiveoptics, reflective optics, and catadioptric systems, for example. Forthe sake of simplicity, the projection system may hereinafter bereferred to as the “lens.” The radiation system may also includecomponents operating according to any of these design types fordirecting, shaping, reducing, enlarging, patterning, and/or otherwisecontrolling the projection beam of radiation, and such components mayalso be referred to below, collectively or singularly, as a “lens.”

Further, the lithographic apparatus may be of a type having two or moresubstrate tables (and/or two or more mask tables). In such “multiplestage” devices, the additional tables may be used in parallel, orpreparatory steps may be carried out on one or more tables while one ormore other tables are being used for exposures. Dual stage lithographicapparatus are described, for example, in U.S. Pat. No. 5,969,441 and PCTApplication No. WO 98/40791, which documents are incorporated herein byreference.

In order to meet the demand for forming ever-smaller components on thedevices produced with lithographic projection apparatus, shorterwavelength radiation (such as EUV radiation) must be used. However,conventional programmable patterning structures may not be suitable foruse with EUV radiation. For example, the surface tension in themultilayer stacks used to reflect EUV light is very high and may bendthe elements in a conventional spatial light modulator.

SUMMARY OF THE INVENTION

In a lithographic apparatus according to one embodiment of theinvention, a programmable patterning structure includes a plurality ofreflective elements. Each reflective element includes upper and lowerdistributed Bragg reflectors having a separation relation selectablefrom among at least a first separation relation and a second separationrelation. When the first separation relation is selected, thereflectivity of the reflective element is relatively low. When thesecond separation relation is selected, the reflectivity of thereflective element is relatively high.

In one such implementation, when the first separation relation isselected, the upper and lower distributed Bragg reflectors arerelatively positioned such that reflections of the projection beaminterfere destructively, and when the second separation relation isselected, the upper and lower distributed Bragg reflectors arerelatively positioned such that reflections of the projection beaminterfere constructively.

In a lithographic projection apparatus according to another embodimentof the invention, a programmable patterning structure includes aplurality of reflective elements, each having a distributed Braggreflector. A position of each of a set of the reflective elements isselectably adjustable to create a phase difference between a reflectionfrom the reflective element and a reflection from another of theplurality of reflective elements.

A device manufacturing method according to a further embodiment of theinvention includes using programmable patterning structure to endow theprojection beam with a desired pattern in its cross-section. Theprogrammable patterning structure includes a plurality of reflectiveelements. Each reflective element includes upper and lower distributedBragg reflectors having a separation relation selectable from among atleast a first separation relation and a second separation relation. Whenthe first separation relation is selected, the reflectivity of thereflective element is relatively low. When the second separationrelation is selected, the reflectivity of the reflective element isrelatively high.

Although specific reference may be made in this text to the use of anapparatus according to an embodiment of the invention in the manufactureof ICs, it should be explicitly understood that such an apparatus mayhave many other possible applications. For example, it may be employedin the manufacture of integrated optical systems, guidance and detectionpatterns for magnetic domain memories, liquid-crystal display panels,thin-film magnetic heads, etc. The skilled artisan will appreciate that,in the context of such alternative applications, any use of the terms“reticle,” “wafer,” or “die” in this text should be considered as beingreplaced by the more general terms “mask,” “substrate,” and “targetportion,” respectively.

In the present document, the terms “radiation” and “beam” are used toencompass all types of electromagnetic radiation, including ultravioletradiation (e.g., with a wavelength of 365, 248, 193, 157 or 126 nm) andEUV (extreme ultra-violet radiation, e.g., having a wavelength in therange 5–20 nm), as well as particle beams, such as ion beams or electronbeams.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in which:

FIG. 1 depicts a lithographic projection apparatus according to anembodiment of the invention;

FIG. 2 depicts a distributed Bragg reflector suitable for use in thepresent invention;

FIG. 3 depicts the use of two distributed Bragg reflectors to create anelement with adjustable reflectivity;

FIG. 4 depicts a portion of a programmable mask according to anembodiment of the present invention;

FIG. 5 depicts a portion of a further programmable mask according to anembodiment of the present invention;

FIG. 6 depicts a portion of a piezoelectric-actuator-driven programmablemask according to an embodiment of the present invention; and

FIG. 7 depicts a portion of an electrostatic-actuator-drivenprogrammable mask according to an embodiment of the present invention.

In the Figures, corresponding reference symbols indicate correspondingparts.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention include a lithographic projectionapparatus with programmable patterning structure suitable for use withEUV radiation.

FIG. 1 schematically depicts a lithographic projection apparatusaccording to a particular embodiment of the invention. The apparatuscomprises:

A radiation system configured to supply (e.g., having structure capableof supplying) a projection beam PB of radiation. In this particularexample, the radiation system Ex, IL for supplying a projection beam PBof radiation (e.g., EUV radiation) also comprises a radiation source LA;

A support structure configured to support a patterning structure capableof patterning the projection beam. In this example, a first object table(mask table) MT is provided with a mask holder for holding a mask MA(e.g., a reticle), and is connected to a first positioning structure foraccurately positioning the mask with respect to item PL;

A second object table (substrate table) configured to hold a substrate.In this example, substrate table WT is provided with a substrate holderfor holding a substrate W (e.g., a resist-coated silicon wafer), and isconnected to a second positioning structure for accurately positioningthe substrate with respect to item PL; and

A projection system (“lens”) configured to project the patterned beam.In this example, projection system PL (e.g., a mirror group) isconfigured to image an irradiated portion of the mask MA onto a targetportion C (e.g., comprising one or more dies) of the substrate W.

The source LA (e.g., a laser-produced or discharge plasma source, or anundulator provided around the path of an electron beam in a storage ringor synchrotron) produces a beam of radiation. The beam is fed into anillumination system (illuminator) IL, either directly or after havingtraversed conditioning structure or field, such as a beam expander Ex,for example. The illuminator IL may comprise an adjusting structure orfield AM for setting the outer and/or inner radial extent (commonlyreferred to as σ-outer and σ-inner, respectively) of the intensitydistribution in the beam, which may affect the angular distribution ofthe radiation energy delivered by the projection beam at, for example,the substrate. In addition, the apparatus will generally comprisevarious other components, such as an integrator IN and a condenser CO.In this way, the beam PB impinging on the mask MA has a desireduniformity and intensity distribution in its cross-section.

It should be noted with regard to FIG. 1 that the source LA may bewithin the housing of the lithographic projection apparatus (as is oftenthe case when the source LA is a mercury lamp, for example), but that itmay also be remote from the lithographic projection apparatus, theradiation beam which it produces being led into the apparatus (e.g.,with the aid of suitable directing mirrors). This latter scenario isoften the case when the source LA is an excimer laser. The currentinvention and claims encompass both of these scenarios.

The beam PB subsequently intercepts the mask MA, which is held on a masktable MT. Having been selectively reflected by the mask MA, the beam PBpasses through the lens PL, which focuses the beam PB onto a targetportion C of the substrate W. With the aid of the second positioningstructure (and interferometric measuring means IF), the substrate tableWT can be moved accurately, e.g., so as to position different targetportions C in the path of the beam PB. Similarly, the first positioningstructure can be used to accurately position the mask MA with respect tothe path of the beam PB, e.g., after mechanical retrieval of the mask MAfrom a mask library, or during a scan. In general, movement of theobject tables MT, WT will be realized with the aid of a long-strokemodule (coarse positioning) and a short-stroke module (finepositioning), which are not explicitly depicted in FIG. 1. However, inthe case of a wafer stepper (as opposed to a step-and-scan apparatus)the mask table MT may just be connected to a short stroke actuator, ormay be fixed. Mask MA and substrate W may be aligned using maskalignment marks M1, M2 and substrate alignment marks P1, P2.

The depicted apparatus can be used in two different modes:

1. In step mode, the mask table MT is kept essentially stationary, andan entire mask image is projected at once (i.e., in a single “flash”)onto a target portion C. The substrate table WT is then shifted in the xand/or y directions so that a different target portion C can beirradiated by the beam PB.

2. In scan mode, essentially the same scenario applies, except that agiven target portion C is not exposed in a single “flash.” Instead, themask table MT is movable in a given direction (the so-called “scandirection,” e.g., the y direction) with a speed v, so that theprojection beam PB is caused to scan over a mask image. Concurrently,the substrate table WT is simultaneously moved in the same or oppositedirection at a speed V=Mν, in which M is the magnification of the lensPL (typically, M=¼ or ⅕). In this manner, a relatively large targetportion C can be exposed, without having to compromise on resolution.

The programmable patterning structure according to one embodiment of thepresent invention includes a plurality of reflective elements arrangedin a grid. For example, each reflective element may have a surface areaof approximately 10 μm×10 μm, and the complete programmable patterningstructure may have a surface area of approximately 25 mm×25 mm. In otherimplementations, the programmable patterning structure may includereflective elements having different aspect ratios and/or surface areasfrom one another.

FIG. 2 shows a distributed Bragg reflector suitable for use in anembodiment of the present invention. The distributed Bragg reflector iscomprised of a multilayer stack 10. In a distributed Bragg reflector foruse with EUV radiation, for example, the stack 10 may include layers 11,13, 15 of molybdenum interposed with layers 12, 14, 16 of silicon. Thehigh reflectivity (of approximately 70%) of the reflector occurs due tothe constructive interference of the radiation reflected from the uppersurfaces 11 a, 13 a, 15 a of the metal layers 11, 13, 15. In order tomaximize the construction of this interference, the distance D1 betweenthe upper surfaces 11 a, 13, 15 a of the metal layers in the directionin which the radiation is directed (i.e., taking into account the angleof incidence) should be a multiple of half of the wavelength λ of theradiation used (e.g., nλ/2, where n is an integer greater than zero).Although the distributed Bragg reflector in FIG. 2 is shown with threemetal layers, it will be appreciated that in practice a much largernumber of layers, for example 80 layers, may be used for optimumreflectivity. Further information on distributed Bragg reflectors may befound in European Patent Publications EP 1,065,532A and EP 1,065,568A,which documents are incorporated herein by reference.

FIG. 3 schematically represents a reflective element of a programmablemask according to an embodiment of the present invention. Theprogrammable mask includes a plurality of reflective elements arrangedon a surface onto which the projection beam of radiation is incident.Each reflective element may be individually controlled, such that bychanging the reflectivity of some of the reflective elements, the beamreflected by the programmable mask contains a desired pattern in itscross-section.

Each reflective element includes two distributed Bragg reflectors 10,20. When the distance D2 between the upper surfaces 15 a, 21 a of themetal layers of the two distributed Bragg reflectors 10, 20 in thedirection of the beam of radiation (i.e., taking account of the angle ofincidence of the beam) is a multiple of half the wavelength of the beamof radiation, the reflections from the two distributed Bragg reflectors10, 20 constructively interfere and the total reflection is at amaximum. When, however, the distributed Bragg reflectors 10, 20 arepositioned such that the distance D2 is altered from the previousposition by a quarter of the wavelength of the radiation, as shown inFIG. 3, then negative (i.e., destructive) interference between thereflection from the upper distributed Bragg reflector 10 and thereflection from the lower distributed Bragg reflector 20 will result insubstantially zero reflectivity of the reflective element.

By adjusting the value of the distance D2 to be in between these twopositions, intermediate levels of reflectivity between zero and themaximum can be attained. Preferably the distance D2 can be adjusted toany one of approximately 200 positions between the positions for themaximum and minimum reflectivity. Alternatively, the position of thedistributed Bragg reflectors may be controlled to allow a continuousrange of settings of distance D2.

Such an arrangement may be used to obtain a programmable patterningstructure in which each reflective element may be controlled to switchbetween relatively high and relatively low reflectivity at a particularwavelength of radiation. Therefore, by setting different reflectiveelements to different states, the programmable patterning structure mayimpart the desired pattern to the beam.

A mask according to an embodiment of the invention may be positionedduring use such that the upper distributed Bragg reflector of areflective element is above a corresponding lower distributed Braggreflector. Alternatively, as shown in FIG. 1, the mask may be positionedduring use such that the upper distributed Bragg reflector of areflective element is actually below a corresponding lower distributedBragg reflector. Of course, the mask may be positioned in many otherorientations as well. For example, the mask may be positioned sidewayssuch that the upper and lower Bragg reflectors of a reflective elementare neither above nor below each other.

An actuator may be used to adjust the separation of the upper and lowerdistributed Bragg reflectors in each reflective element according to oneof a plurality of positions. For example, the actuator may set thereflectivity of the reflective element to be at a selected one of aplurality of levels between the first position, in which thereflectivity is substantially zero, and the second position, in whichthe reflectivity is a maximum. Such actuated control of a plurality oflevels may facilitate better control of the pattern imparted to theprojection beam.

In another implementation, two or more of the reflective elements have acommon first distributed Bragg reflector. For example, such anarrangement may result in a programmable patterning structure that ismore easily manufactured. In one such implementation, the reflectivityof a reflective element is set by moving the corresponding seconddistributed Bragg reflector relative to the common first distributedBragg reflector.

In an exemplary implementation of a lithographic apparatus according toan embodiment of the invention, the projection beam of radiation is EUVradiation, and the distributed Bragg reflectors are designed to beindividually reflective of EUV radiation at the wavelength used.Additionally, the difference in the separation of the first and seconddistributed Bragg reflectors between the positions of zero and maximumreflectivity is approximately one-quarter of the wavelength of theradiation used. Such an arrangement provides a greater degree ofcontrast between the reflective elements' maximum and minimumreflectivity.

FIG. 4 schematically shows three reflective elements A, B, C of aprogrammable mask according to an embodiment of the present invention.Reflective element A includes two distributed Bragg reflectors 31, 32,as described before and a piezoelectric actuator 33. Similarly,reflective element B includes distributed Bragg reflectors 34, 35 andpiezoelectric actuator 36, and reflective element C includes distributedBragg reflectors 37, 38 and piezoelectric actuator 39. By applyingappropriate voltages to the individual piezoelectric actuators 33, 36,39, the position of the lower distributed Bragg reflectors 32, 35, 38may be moved relative to the corresponding upper distributed Braggreflectors 31, 34, 37, respectively, thereby altering the reflectivityof each of the reflective elements A, B, C.

As noted above, the separation of the upper and lower distributed Braggreflectors may be adjusted using a piezoelectric actuator. Theperformance of such actuators is well understood, and it is possible tocontrol the movement of such piezoelectric actuators to a very highlevel of accuracy. Such accuracy may be required since, for a typicalEUV application, the range of movement of the piezoelectric actuator maybe on the order of a few nanometers with a required accuracy in thesub-nanometer range. For example, to provide 10 grey levels between thefirst and second positions in such an application, the differencebetween the separation at adjacent positions may be approximately 0.2 to0.5 nm.

As shown in FIG. 4, each of the reflective elements A, B, C has adiscrete piezoelectric element 33, 36, 39, respectively. However, inanother implementation, two or more of the reflective elements may havea common piezoelectric element. The piezoelectric effect is generallylimited to a region immediately surrounding the voltage applied to apiezoelectric element. Therefore, by providing the voltage only to aregion of the common piezoelectric element that corresponds to aparticular reflective element, only the lower distributed Braggreflector corresponding to that reflective element may be moved, therebyadjusting the reflectivity only of that reflective element. Thus, byattaching a plurality of electrodes to a single piezoelectric elementthat controls the positions of multiple lower distributed Braggreflectors, a plurality of reflective elements sharing the piezoelectricelement can be controlled.

FIG. 5 depicts a further variant of this embodiment. Each of thereflective elements D, E, F has its own lower distributed Braggreflector 42, 45, 48, the position of which may be adjusted withcorresponding piezoelectric actuators 43, 46, 49. In this case, however,the reflective elements D, E, F share a common upper distributed Braggreflector 41. Depending on the size of the programmable mask, the upperdistributed Bragg reflector 41 may be common to all the reflectiveelements in the programmable mask or just to a section of it. As before,two or more reflective elements may be arranged to share a commonpiezoelectric element. For example, using a common piezoelectric elementmay significantly simplify the production of a programmable patterningstructure.

FIG. 6 shows the embodiment of FIG. 4 in more detail. The upperdistributed Bragg reflector 51 of each reflective element A, B, C issupported by supports 54, 55. As shown in FIG. 6, the supports may becolumns between the reflective elements A, B, C. Alternatively, amesh-like structure may be formed onto which the upper distributed Braggreflectors 51 are placed. The lower distributed Bragg reflectors 52 aresupported on a piezoelectric layer 53. The gap 58 between the upper andlower distributed Bragg reflectors may be filled with a porous material(provided it is substantially transparent to the beam of radiation) ormay be a vacuum.

The piezoelectric element 53 has upper and lower electrodes 56, 57,respectively, to provide the voltage to actuate the piezoelectricactuators and thereby alter the size of the gap 58 between the upper andlower distributed Bragg reflectors. The upper electrode layer 56 may becommon for all the reflective elements, the actuation signal beingprovided via the lower electrode layer 57. Alternatively, the lowerdistributed Bragg reflector may be used as the top electrode. Asdiscussed before, the upper distributed Bragg reflector and/or thepiezoelectric element (or portions thereof) may be common for some orall of the reflective elements.

As a further alternative, the separation of the upper and lowerdistributed Bragg reflectors may be adjusted by electrostatic actuation.Such an arrangement may reduce the complexity of the programmablepatterning structure and facilitate its manufacture, for example, usingsuch actuation in place of piezoelectric elements.

FIG. 7 depicts an alternative embodiment of the present invention inwhich the upper and lower distributed Bragg reflectors 61, 62 are usedas electrodes to adjust the distance between the distributed Braggreflectors using electrostatic attraction. In one such arrangement, thesupport 64, 65 is used to provide the signals to the distributed Braggreflectors, and the gap 68 between the distributed Bragg reflectors iselectrically non-conductive. As above, the gap 68 may be a vacuum or maybe filled with a porous (and substantially transparent) material.

In a particular arrangement as shown in FIG. 7, as the electrostaticforce between the two distributed Bragg reflectors 61, 62 increases, thesupports 64, 65 bend, varying the separation between the distributedBragg reflectors.

A potential advantage of using electrostatic actuation is that suchactuation may be implemented to operate at potentials lower than thetens of volts that may be needed to produce a required movement ofpiezoelectric elements.

Whilst specific embodiments of the invention have been described above,it will be appreciated that the invention as claimed may be practicedotherwise than as described. It is explicitly noted that the descriptionof these embodiments is not intended to limit the invention as claimed.

1. A programmable patterning structure configured to pattern a beam ofradiation, the programmable patterning structure comprising: a pluralityof reflective elements, each reflective element including a distributedBragg reflector, wherein the programmable patterning structure includesat least one piezoelectric element configured to adjust a position of atleast one of a set of the plurality of reflective elements to create aphase difference between a reflection from the at least one reflectiveelement and a reflection from another of the plurality of reflectiveelements.
 2. The structure of claim 1, wherein the piezoelectric elementis configured to adjust a position of each of the set of the pluralityof reflective elements between a first position and a second position,such that when the reflective element is in the first position, areflection from the reflective element interferes destructively with areflection from another of the plurality of reflective elements, andsuch that when the reflective element is in the second position, areflection from the reflective element interferes constructively with areflection from the other of the plurality of reflective elements. 3.The structure of claim 1, wherein a difference in the distance between areflecting layer of the reflective element and a reflecting layer of theother of the plurality of reflective elements between the first andsecond positions is substantially equal to one-quarter of a wavelengthof the beam of radiation.
 4. The structure of claim 1, wherein thepiezoelectric element is configured to adjust a position of each of theset of the plurality of reflective elements between the first position,the second position, and at least one position between the first andsecond positions.
 5. The structure of claim 1, wherein saidpiezoelectric element is common to at least two of the plurality ofreflective elements, wherein each of said at least two reflectiveelements includes an electrode configured to apply a signal to cause apiezoelectric effect in the piezoelectric element that is substantiallylocal to the reflective element.
 6. The structure of claim 5, wherein acommon electrode is disposed on one side of the piezoelectric element,said common electrode being common to the at least two reflectiveelements, and wherein the electrode of each of the said at least tworeflective elements is disposed on a second side of the piezoelectricelement, said second side being opposite to said first side.
 7. Thestructure of claim 1, wherein the Bragg reflectors include a multilayerstack of Silicon and Molybdenum.
 8. The structure of claim 1, wherein agap separating the at least one of a set of the plurality of reflectiveelements from the other of the plurality of reflective elements isfilled with a porous material that is substantially transparent at awavelength of said radiation beam.
 9. The structure of claim 1, whereinsaid structure is configured to continuously adjust a gap separating theat least one of a set of the plurality of reflective elements from theother of the plurality of reflective elements.
 10. The structure ofclaim 1, wherein each of the Bragg reflectors has a substantially squareshape.
 11. The structure of claim 1, wherein each reflective elementincludes an upper and lower distributed Bragg reflectors and whereineach of the lower distributed Bragg reflectors includes a piezoelectricelement.
 12. The structure of claim 1, wherein the piezoelectric elementincludes an electrode arranged on one side of the piezoelectric element.13. The structure of claim 1, wherein each piezoelectric elementincludes an upper and a lower electrode that are disposed on oppositesides of the piezoelectric element.
 14. A programmable patterningstructure configured to pattern a beam of radiation, the programmablepatterning structure comprising: a plurality of reflective elements,each reflective element including upper and lower distributed Braggreflectors having a separation relation selectable from among at least afirst separation relation and a second separation relation, and anactuator configured to set a separation relation of at least one of thereflective elements to one of the first separation relation, the secondseparation relation, and at least one separation relation between thefirst and second separation relations, wherein, when the firstseparation relation is selected, a reflectivity of the reflectiveelement at a wavelength of the beam of radiation is relatively low, andwhen the second separation relation is selected, a reflectivity of thereflective element at a wavelength of the beam of radiation isrelatively high, and wherein the actuator includes a piezoelectricelement.
 15. The structure of claim 14, wherein at least two among theplurality of reflective elements have a common distributed Braggreflector.
 16. The structure of claim 15, wherein the common distributedBragg reflector is configured to be locally distortable such that aselected position of the common distributed Bragg reflector differsbetween the at least two among the plurality of reflective elements. 17.The structure of claim 14, wherein, when the first separation relationis selected, the upper and lower distributed Bragg reflectors arerelatively positioned such that reflections of the beam of radiationinterfere destructively, and wherein, when the second separationrelation is selected, the upper and lower distributed Bragg reflectorsare relatively positioned such that reflections of the beam of radiationinterfere constructively.
 18. The structure of claim 14, wherein atleast two of the plurality of reflective elements have a common upperdistributed Bragg reflector.
 19. The structure of claim 14, wherein adifference in the distance between a reflecting layer of the upperdistributed Bragg reflector and a reflecting layer of the lowerdistributed Bragg reflector between the first and second separationrelations is substantially equal to one-quarter of a wavelength of thebeam of radiation.
 20. The structure of claim 14, wherein thepiezoelectric element is common to a set including at least two of thereflective elements, and wherein each reflective element of the setincludes an electrode configured to apply a signal to cause apiezoelectric effect in the piezoelectric element that is substantiallylocal to the reflective element.
 21. The structure of claim 20, whereina common electrode is disposed on one side of the piezoelectric element,said common electrode being common to the at least two reflectiveelements, and wherein the electrode of each of the said at least tworeflective elements is disposed on a second side of the piezoelectricelement, said second side being opposite to said first side.
 22. Thestructure of claim 14, wherein at least one of the plurality ofreflective elements is configured to use an electrostatic force toadjust a separation relation between the upper and lower distributedBragg reflectors.
 23. The structure of claim 14, wherein the Braggreflectors include a multilayer stack of Silicon and Molybdenum.
 24. Thestructure of claim 14, wherein a gap separating the upper and lowerdistributed Bragg reflectors is filled with a porous material that issubstantially transparent at a wavelength of said radiation beam. 25.The structure of claim 14, wherein said structure is configured tocontinuously adjust a gap separating the upper and lower distributedBragg reflectors.
 26. The structure of claim 14, wherein each of theBragg reflectors has a substantially square shape.
 27. The structure ofclaim 14, wherein each of the plurality of reflective elements isindependently controlled to select the separation relation.
 28. Thestructure of claim 14, wherein a relatively high reflectivity is about70%.
 29. The structure of claim 14, wherein each of the lowerdistributed Bragg reflectors includes a piezoelectric element.
 30. Thestructure of claim 14, wherein each of the piezoelectric elementsincludes an electrode arranged on one side of the piezoelectric element.31. The structure of claim 14, wherein each of the piezoelectric elementincludes an upper and a lower electrode that are disposed on oppositesides of the piezoelectric element.